Acoustical cabinet for loudspeakers



Feb. 16', 1965 R. M. SMITH AcousTcAL CABINET FOR LoUDsPEAKEzRs 2Sheets-Sheet 1 Filed June 28, 1963 Feb. 16, 1965 R. M. SMITH ACoUs'rIcALCABINET FOR LouDsPEAKERs Filed June 28. 1963 Fig. 4

2 Sheets-Sheet 2 Richard M. Smith INVENTOR.

United States Patent O 3,169,601 ACOUSTICAL CABINET FOR LOUDSPEAKERSRichard M. Smith, 318 6th St., Greenport, N.Y. Filed June 28, 1963, Ser.No. 291,416 4 Claims. (Cl. 181-31) This invention relates to soundreproducing apparatus and more particularly to an acoustical cabinetwhich increases or amplies the sound radiating output of a loudspeaker.The principles underlying operation of the present invention are similarto those disclosed in my prior copending application U.S. Serial No.137,655, tiled September 12, 1961, now U.S. Patent 3,115,208.

It is therefore a primaly object of the present invention to provide animproved loudspeaker cabinet particularly suitable for mounting of smalland inexpensive loudspeakers of the radiating cone type so as to producea speaker system of unexpectedly high efficiency and acceptably faithfulreproduction characteristics. The output range from the acousticalcabinet of the present invention is therefore comparable in performanceto that of the more expensive speaker systems and wherein the acousticalcabinet occupies a significantly larger volume and/ or door space.

The principle underlying the demonstrated successful results obtainedwith the acoustical cabinet of the present invention, may beattributable to the vibration-free mounting of the loudspeaker on a bafemember which separates the enclosure into a front and rear chambersimilar to the arrangement disclosed in the aforementioned priorcopending application. Thus, optimum results have been obtained throughexperimentation with such an equal volume relationship, this beingpossibly attributable to the relative loading of the radiating cone orcones of the loudspeakers both forwardly and rearwardly thereof becauseof the recessing of the speaker mounting member so as to produce acushioning effect on the speaker diaphragm, eliminating mingling ofysound and approaching the theoretically perfect speaker bafflingarrangement. The acoustical cabinet is also provided w-ith a vented backpanel providing compressional relief vents for the rear chamber in orderto avoid stiifening of the speaker diaphragm or cone. In order tofurther improve and enhance operation of the speaker system, theacoustical cabinet device of the present invention further includespassages surrounding the front and rear chambers and separated therefromso as to establish passages between the open lfront of the acousticalcabinet and the` rear chamber adj acent the back panel. It has thereforebeen found, that the additional venting for the rear chamber andpassageways formed about the chambers conducting sound energy toward theopen front, reinforces the output from the forwardly radiating speakerorspeakers mounted on the bafe member. p

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIGURE 1 is a perspective View of the acoustical cabinet device of thepresent invention as seen from the front.

FIGURE 2 is -a perspective view of the acoustical cabinet as seen fromthe rear.

FIGURE 3 is a front elevational View of the speaker cabinet with thefront grille removed.

FIGURE 4 is a rear elevational View of the speaker cabinet with the backpanel removed.

FIGURE 5 is a top sectional View through the speaker cabinet takensubstantially through a plane indicated by section line 5 5 in FIGURE l.

FIGURE 6 is -a transverse sectional view through the speaker cabinettaken through a plane indicated by section line 6 6 in FIGURE l.

Referring now to the drawings in detail, one exemplary form of speakercabinet is illustrated in FIGURES l and 2 generally referred to byreference numeral 10. The cabinet encloses an outer chamber 11 dened byinterconnected outer walls including parallel spaced t-op wall 12 andbottom wall 14 interconnected by side walls 16 and 18. All of theinterconnected walls are rectangular in shape defining a completely openrectangular front which may be covered by a grille 20 while a back panel22 is secured in place in the rear opening of the cabinet enclosure. Thecabinet may be mounted in any suitable manner and 'at any suitablelocation as for example by the legs 24 spacing the enclosure above asupporting floor.

As more clearly seen in FIGURES 3-6, the outer walls of the cabinet arerigidly interconnected with the top and bottom walls 12 and 14 beingdisposed in edge-abutting relation to the side walls 16 and 18. Thesewalls are formed from a vibration-dampening material such as a materialmarketed under the name of Homasote, cut from panels preferably one inchin thickness. A decorative veneer 26 may be cemented in place on theexternally exposed surfaces of the outer walls in a manner well known.The back panel 22 is also formed of the same vibration-dampeningmaterial and isisecured in place by a pair of mounting strips 28 securedto the rear edges of the top and bottom walls 12 and 14. The back panelis dimensioned so that when it is mounted within the back opening of thecabinet enclosure, it will be equally spaced from'the top and bottomwalls and side walls providing -a continuous peripheral vent opening 30.The back panel may therefore be imperforate except for the mountingtherein of Vany components associated with the speaker system such asthe volume control element 32 .and the terminal connection element 34 asseen in FIGURES 2 and 5.

Also associated with the speaker system, will be one or moreloudspeakers including a main speaker 36 of the radiating cone typehaving a driver portion 38 through which electricalenergy isv convertedinto mechanical energy vibrating the cone portion 40 for radiating soundenergy both forwardly and rearwardly therefrom. The main loudspeakerunit 36 is therefore mounted together with other speaker components 42and 44 if utilized on a baffle member 46 provided with openingsreceiving the sound radiating cone or horn if this type of auxiliaryspeaker unit is utilized. The baiile member 46 is otherwise imperforateand secured in place by side passage members 4S and 50 and top andbottom passage members 52 and 54. The side passage members 48 and 50 aredisposed in equal spaced parallel relation to the side walls 16 and 18so as to define side passages 56 and 58 whilek the members 52 and 54 arerespectively disposed parallel to the top and bottom walls 12 and 14 soas to dene top and bottom passages 60 and 62. The passage members arealso made of the same sound-dampening materialv mentioned in connectionwith the outer wall members and enclose an inner chamber 13 including afront chamber portion 64 and a rear chamber portion 66 on opposite sidesof the baffle member 46. The baffle member is secured within the passagemembers so as to separate the front and rear chamber portions intosubstantially equal Volumes. The front chamber portion 64 thereforeextends `from the baie member forwardly to the open front end of thecabinet so that forwardly radiating sound energy Ifrom the speaker coneswill emanate therefrom. The rear chamber .portion 66 on the other hand,extends from the baiile member rearwardly terminating in spacedadjacency to the back panel 22. The rear chamber portion 66 is thereforeinv uid communication with the open front end by means of the rear spaceS and passages 56, 58, 60 and 62 which completely surround the front andrear chamber portions. Sound radiated by the speaker diaphragms in arearward direction will cause compression and rarefaction of the airwithin the outer chamber which will be vented by the vent opening 3i)while some of the sound energy itself may be reected by the back paneland passed through the surrounding passages out through the open frontfor reinforcing the forwardly radiating sound energy.

The dimensions of the various parts forming the speaker enclosure areselected in accordance with the foregoing constructional principlesamongst which there is the equal volume requirement for the front andrear chamber portions 634 and 66, the formation of a vent opening 30 inthe rear opening of the enclosure and the size of the main speaker 36.

From the foregoing description, the construction, operation and utilityof the acoustical cabinet device of the `present invention will beapparent. The dimensions of the cabinet are critical only in connectionwith the equal volumes of the front and rear chamber portions, relativeto dimensions of the surrounding passages and rear vent opening. Also,the selection of a sound-dampening material for the enclosure walls andchamber walls as well as for the speaker mounting baiiie member, areimportant. Also important is the open front arrangement so that soundwaves radiated forwardly from the speaker may diverge withoutobstruction while the rearwardly radiated sound energy is partiallyreflected while the vent opening 30 provides compressional relief so asto avoid cone stiifening. Also, the relative loading of the speaker coneboth forwardly and rearwardly produces the aforementioned cushioningeffect by virtue of which the extended volume range of the speakersystem is attained utilizing less costly and smaller speaker units aswell as a dimensionally less extensive speaker cabinet.

The `foregoing is considered as illustrative only 'of the the principlesof the invention. Further, since numerous modications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents maybe resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. An acoustical cabinet for a loudspeaker havingVA a sound radiatingelement comprising, interconnected outer walls forming an outer chamberextending between a completely open -front end and a rear end, insidewalls connected to said outer walls forming an innerchamber portioncross-sectionally larger throughout than the sound radiating element andextending from said front end a distance short of the rear-end, saidinner chamber portion being spaced from the outer walls to formsurrounding passageways extending` rearwardly from said front end,

a baille member. connected to the insidel Walls completely ,dividingsaid inner chamber portion into substantially equal parts, said bafliemember having an opening therein mounting the sound radiating element ofthe loudspeaker, a rigid back panel substantially closing the outerchamber at the rear end, and means securing said back panel in spacedrelation to the outer walls to form a peripheral vent opening for theouter chamber aligned with said passageways.

2. The combination of claim 1 wherein said walls are made from ilatpanels of vibration-dampening material to form the inner and outerchamber rectangular in crosssectional area.

3. An acoustical cabinet in combination with a loudspeaker having aradiating cone comprising, an enclosure having walls defining anelongated chamber cross-sectionally larger than the radiating cone, arigid back panel, an imperforate baiiie member supporting theloudspeaker thereon, means secured to said Walls for mounting the balliemember intermediate opposite ends of the chamber and forming front and`rear chamber portions on opposite sides of the baflie member to load theradiating cone both forwardly and rearwardly within the enclosure, saidwalls of the enclosure being formed of vibration-dampening materialenclosing said front and rear chamber portions, one of said oppositeends of the chamber being completely open and acoustically unobstructed,means securing said rigid back panel to the enclosure at the other ofthe opposite ends in spaced relation to the walls to form compressionalrelief vents rearwardly spaced from the rear chamber portion, and soundpassage means externally surrounding the baflie member and isolated fromsaid front and rear chamber portions within the enclosure establishingcommunication between the open end and the rear chamber portion adjacentthe back panel, said rear chamber portion terminating in spacedadjacency to said relief vents.

4. The combination of claim 3 wherein said passage means is formed bychamber forming members disposed in spaced parallel relation to thewalls of the enclosure and made of said vibration-dampening material.

References Cited'by the Examiner UNITED STATES PATENTS 1,843,524 2/32Stenger 181-31 1,866,921 7/32 Black 181-31 2,062,515 12/ 36 Hoschke181-27 2,160,284 5/39 Roberts 181-31 2,167,625 8/39 Albano 181-312,730,302 2/57 George 181-31 2,780,302 2/57 George 181-31 3,072,212 1/63Chapman 181-31 FOREIGN PATENTS 843,643 4/ 39 France. 908,709 10/45France.

LEO SMILOW, Primary Examiner.

LEYLAND M. MARTIN, Examiner.

1. AN ACOUSTICAL CABINET FOR A LOUDSPEAKER HAVING A SOUND RADIATINGELEMENT COMPRISING, INTERCONNECTED OUTER WALLS FORMING AN OUTER CHAMBEREXTENDING BETWEEN A COMPLETELY OPEN FRONT END AND A REAR END, INSIDEWALLS CONNECTED TO SAID OUTER WALLS FORMING AN INNER CHAMBER PORTIONCROSS-SECTIONALLY LARGER THROUGHOUT THAN THE SOUND RADIATING ELEMENT ANDEXTENDING FROM SAID FRONT END A DISTANCE SHORT OF THE REAR END, SAIDINNER CHAMBER PORTION BEING SPACED FROM THE OUTER WALLS TO FORMSURROUNDING PASSAGEWAYS EXTENDING REARWARDLY FROM SAID FRONG END, ABAFFLE MEMBER CONNECTED TO THE INSIDE WALLS COMPLETELY DIVIDING SAIDINNER CHAMBER PORTION INTO SUBSTANTIALLY EQUAL PARTS, SAID BAFFLE MEMBERHAVING AN OPENING THEREIN MOUNTING THE SOUND RADIATING ELEMENT OF THELOUDSPEAKER, A RIGID BACK PANEL SUBSTANTIALY CLOSING THE OUTER CHAMBERAT THE REAR END, AND MEANS SECURING SAID BACK PANEL IN SPACED RELATIONTO THE OUTER WALLS TO FORM A PERIPHERAL VENT OPENING FOR THE OUTERCHAMBER ALIGNED WITH SAID PASSAGEWAYS.